1. Field of Invention
The present invention relates to an optical disk recording apparatus for recording data and forming a visible image with respect to an optical disk such as a CD-R.
2. Description of Related Art
A helical guide groove called a groove is provided in an optical disk such as a CD-R (Compact Disk-Recordable). When data is recorded, high-level laser light is intermittently applied along this groove, and a recording layer is thereby discolored to form marks. At the time of reproduction, low-level laser light is applied along the groove. The reflected light level of the laser light does not change much in a land where the mark has not been formed, but the reflected light level of the laser light declines in a portion where the mark has been formed. Therefore, by determining whether or not the level of the reflected light is at a fixed reference level or higher, it becomes possible to reproduce data. It should be noted that the mark referred to herein means one which has an effect optically equivalent to an embossed pit in an optical disk for reproduction only.
Meanwhile, in recent years, in addition to the technique of recording data, a technique of forming a visible image has also been proposed. In this technique, the mark in a rendering area is formed by being corrected so as to become thicker (or thinner) than the mark in a non-rendering area. The reflectivity of the rendering area is thereby made different from that of the non-rendering area, and a visible image is represented by using this difference in reflectivity (e.g., refer to patent documents 1 and 2).
Patent Document 1
JP-A-09-312021
Patent Document 2
JP-A-11-134648
Incidentally, in the optical disk, data is recorded in the EFM (Eight to Fourteen Modulation) format so that the marks or lands will not continue, it should naturally suffice if the laser is turned on and off in accordance with the EMF data. However, to form the marks in accurate lengths, it is common practice to correct the irradiation timing of the laser light in accordance with a conversion rule (correction rule) called a strategy. For this reason, a scheme was conceived for changing over the strategy between the rendering area and the non-rendering area.
However, since the mark forming operation and the image forming operation are essentially unrelated to each other, cases can occur in which the rendering area is changed over to the non-rendering area during the formation of marks in the rendering area in accordance with the rendering rule, or in which the non-rendering area is conversely changed over to the rendering area during the formation of marks in the non-rendering area. In such a case, the strategy is also changed over suddenly, with the result that discontinuous bits are formed. Hence, a drawback has been pointed out in that a read error is induced.